From 934e6ebf96e8c1a0f299e64129fdaebc1132a427 Mon Sep 17 00:00:00 2001 From: Alan Cox Date: Mon, 13 Oct 2008 10:40:43 +0100 Subject: tty: Redo current tty locking Currently it is sometimes locked by the tty mutex and sometimes by the sighand lock. The latter is in fact correct and now we can hand back referenced objects we can fix this up without problems around sleeping functions. Signed-off-by: Alan Cox Signed-off-by: Linus Torvalds --- drivers/char/tty_io.c | 18 ++++-------------- 1 file changed, 4 insertions(+), 14 deletions(-) (limited to 'drivers/char') diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c index b5f57d0..f40298e 100644 --- a/drivers/char/tty_io.c +++ b/drivers/char/tty_io.c @@ -739,13 +739,11 @@ void tty_vhangup_self(void) { struct tty_struct *tty; - mutex_lock(&tty_mutex); tty = get_current_tty(); if (tty) { tty_vhangup(tty); tty_kref_put(tty); } - mutex_unlock(&tty_mutex); } /** @@ -801,11 +799,9 @@ void disassociate_ctty(int on_exit) struct pid *tty_pgrp = NULL; - mutex_lock(&tty_mutex); tty = get_current_tty(); if (tty) { tty_pgrp = get_pid(tty->pgrp); - mutex_unlock(&tty_mutex); lock_kernel(); if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY) tty_vhangup(tty); @@ -822,7 +818,6 @@ void disassociate_ctty(int on_exit) kill_pgrp(old_pgrp, SIGCONT, on_exit); put_pid(old_pgrp); } - mutex_unlock(&tty_mutex); return; } if (tty_pgrp) { @@ -837,7 +832,6 @@ void disassociate_ctty(int on_exit) current->signal->tty_old_pgrp = NULL; spin_unlock_irq(¤t->sighand->siglock); - mutex_lock(&tty_mutex); tty = get_current_tty(); if (tty) { unsigned long flags; @@ -854,7 +848,6 @@ void disassociate_ctty(int on_exit) " = NULL", tty); #endif } - mutex_unlock(&tty_mutex); /* Now clear signal->tty under the lock */ read_lock(&tasklist_lock); @@ -3180,14 +3173,11 @@ static void proc_set_tty(struct task_struct *tsk, struct tty_struct *tty) struct tty_struct *get_current_tty(void) { struct tty_struct *tty; - WARN_ON_ONCE(!mutex_is_locked(&tty_mutex)); + unsigned long flags; + + spin_lock_irqsave(¤t->sighand->siglock, flags); tty = tty_kref_get(current->signal->tty); - /* - * session->tty can be changed/cleared from under us, make sure we - * issue the load. The obtained pointer, when not NULL, is valid as - * long as we hold tty_mutex. - */ - barrier(); + spin_unlock_irqrestore(¤t->sighand->siglock, flags); return tty; } EXPORT_SYMBOL_GPL(get_current_tty); -- cgit v1.1